feat(windows): replace Qt frontend with React/Tauri

[1lck]

Summary

• replace the Windows Qt/C++ product with the Athas-derived React/Tauri frontend
• preserve the macOS Swift frontend and route shared deterministic behavior through rust/lithe-core
• add the TypeScript/Tauri platform boundary, Core-backed search, Git, local history, and LSP adapters
• move Windows-native terminal, process, watcher, credentials, window, clipboard, and packaging behavior into the Tauri host
• capability-gate future shared features such as AI, SSH, WSL, database, Docker, GitHub, debugger, and extension installation
• update Windows CI, release, build, packaging, architecture, and boundary verification

Validation

• bun install --frozen-lockfile
• bun typecheck
• bun run build
• cargo fmt --manifest-path rust/lithe-core/Cargo.toml -- --check
• cargo test --manifest-path rust/lithe-core/Cargo.toml
• cargo test --manifest-path windows/tauri/src-tauri/Cargo.toml
• ./scripts/verify-shared-contracts.sh
• ./scripts/verify-rust-core.sh
• ./scripts/verify-windows-boundaries.sh
• git diff --check

Windows verification remaining

This change was prepared and validated on macOS. WebView2, ConPTY, Windows installer generation, code signing, updater behavior, and the real Windows UI still require Windows CI/device verification.